Such functional lighting instruments as street lamps and tunnel lamps require that each point within the illuminated zone has luminance that must meet the minimum luminance indicator, the maximum glare requirement indicator, the light intensity uniformity index, and the illuminated zone restriction requirement required by the lighting specification, and also have high requirements on reliability, energy saving, environmental protection and other performances of the products. The existing street lamps and tunnel lamps widely have a problem that the light irradiated to the ground has poor luminance uniformity. To improve the lighting effect and protect health of the human eye, lamps must be utilized for lighting configuration of the optical system; that is, a light field of uniform luminance is provided by light irradiation at a specified road position and within a given road zone, with the light irradiated outside the specified zone considered to be invalid.
The existing LED lamps widely have a problem that the heat produced during work cannot be dissipated timely and is likely to cause heat accumulation, with a lot of heat produced during long hours of work easily causing such negative phenomena as fading of light of the LED lamp, thereby affecting lifetime of the LED lamp. Some of the LED lamps are used in outdoor environment and thus may be affected with damp in the rain, wind and snow weather, and the circuit boards inside the LED lamps are easy to get short circuit caused by water vapor to thus make the LED lamps burnt and so on.
Besides, for the traditional LED lamps, all the LED lamp beads thereon are arranged on a piece of LED circuit board having a large area and a planar plate shape, where these LED lamp beads can only be placed in the same plane and the light emitted by each of the lamp beads may overlap in a wide range in the air. As a result, in a target illuminated zone, some places are very dark because only a small part of the light is projected over, while other places are very bright because a big part of the light is projected over, thus resulting in very obvious light spots in the target illuminated zone and very poor irradiation uniformity. Then a sufficient number of LED lamp beads and large enough luminous power have to be used to make each place of the target illuminated zone get the required light intensity, thus exhausting a great deal of electric power.